I have been through the McMasterCarr with No luck. I am looking for a way to couple a motor; modified servo or a pager motor without its counter weight, both have Very small diameter shafts, don`t know exactly the dia. Anyways I would like to couple the motor to a drive shaft. Again the drive shaft is 1/8" dia. I have seen a version from the U.K that has a connector on the motor and seperate one on the drive shaft and is connected by a rubber type tube that pushes onto each end connector, thise connectors are secured with set screws. Unfortunately the U.K prices are high and there are No quantity discounts.

The motors would be 5000 RPM or higher, best guess.

Does anyone know of a U.S or Canada Source for such a coupler fitting?

My recommendation is to get the Delrin and brass hub version(s). If you do not find the exact shaft combination that you need, you can always take the universals apart and recombine them into the two shaft sizes that your application requires. (e.g. buy a 1/8-inch-to-1/8-inch and a 3mm-to-3mm and then end up with a pair of 1/8-inch-to-3mm universals)

George - do you still have your lathe/mill? Why not just turn out an adapter piece that will attach to the motor shaft with a set-screw and allow you to press-fit a piece of tube over the other end to act as your universal. Same goes for the 1/8 dia drive shaft end.